A Country Watch Tower, such as you might find in Whitecastle or Candlemere, serves as a permanent base for the patrol Marshals who are located in the area. While there are a few resident troops to secure the barracks and operate local patrols, they are not really intended to be a town watch. However, they will add to the defence of a village or town, if it comes under attack. While they will support the local mayor / ruler - they are not policemen.